Nonsense that is involved in change, sapping power and enthusiasm (10)
I believe the answer is:
ebullience
'enthusiasm' is the definition.
(synonyms)
'nonsense that is involved in change sapping power and' is the wordplay.
I cannot quite see how this works, but
'nonsense' could be 'bull' (I've seen this before) and 'bull' is found in the answer.
'and' could be 'n' (common abbreviation for 'and') and 'n' is found within the answer.
'that is' could be 'ie' (abbreviation for id est, 'that is' in Latin) and 'ie' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for ebullience that I've seen before include "Enthusiastic excitement" , "Exuberance" , "Cheerful enthusiasm; boiling over" .)